EN
For the manganites Pr_{0.5}Ca_{0.5-x}Sr_xMnO_3 (x=0;0.3) the temperature and cooling field dependence of the reduced remanence asymmetry indicates the antiferromagnetic exchange between the antiferromagnetic and ferromagnetic spins at the surface of the clusters. For x=0.3 we deduce the radius of the cluster in the field cooled regime to be about 20 times larger than that for x=0.